1997 3.0, intermittent start, now no start- stumped?

[cstarbard]

Hey guys,

Posting on behalf of my brother but am also a long time Ranger fan.

He just got a beautiful 1997 3.0 4x4 which we love, but we're having a real time getting it to start and it has me stumped. Any help would be great!!

When we got the truck, it didn't start great, meaning it cranked a lot before firing. It continued to crank more and more before starting, sometimes not starting at all for many attempts, but always eventually starting if you tried long enough. It also began to feel a little gutless overall.

We changed the fuel pump, one fuel line, and the filter, and it started more consistently after that, but still sometimes cranked over for longer than seems necessary.

Last night, he was driving it, running fine. Then it started bucking hard and running like really farty and weird, as if there was a serious lack of fuel or a hard misfire. 5 seconds later, basically normal again, and we parked it, shut it off, got dinner.

Could not get that thing started again at all and got towed home.

It cranks over really fast, so we know the battery is good. The starter is clearly turning it over with ease so I think we can also rule that out.

We changed the coil pack (which also has the icm built in, correct?)- still nothing.

I pulled a fuel pressure regulator off a 2.3 in our backyard, swapped it, and it started up perfectly, and ran fine. But, after I shut it off, its back to the no start condition? Tried several other regulators, same thing: coughs, starts and quits, or doesnt start. Every time this happens there is plenty of fuel in the regulator and in the rail, which you can see when you remove regulator.

We tripped and un tripped the inertia switch many times, still no change.

What gives??

MY thoughts are:

Easy stuff- check the fuel pump relay and fuses associated with that or inertia switch? Swap inertia switch and connector, check fuel pressure at the rail, bleed it at the rail..? check wires at fuel pump

Any other help would be greatly appreciated.

Chris

 

[cstarbard]

Also, we don't see evidence of a fuel leak anywhere between tank and engine, so I'm thinking we can rule that out as well.

 

[cstarbard]

It also starts and runs briefly on starting fluid, so spark must be ok

 

[RonD]

Welcome to TRS

You have done some good tests, since it starts instantly when you add fuel manually to the intake then yes, it would be my guess you have a fuel delivery problem.

In 1995 and up Rangers use the newer EEC-V computer, it has the built-in ICU, coil pack is just 3 coils in a pack, each coil sparks two spark plugs at the same time.

Simple test would be to crank cold engine a few times
Pull out 1 or 2 spark plugs and look at the tips, they should be WET with fuel, if not then fuel injectors are not opening or there is not enough fuel pressure at the injectors.

For further fuel test I would hook a test light up to Inertia switch(either terminal) and a Ground.
When you first turn on the key you should see the test light come on for 2 seconds then go off, this is the computer closing the Fuel Pump Relay for 2 seconds to Prime the fuel system, then shuts off FP Relay until engine starts, above 400 RPMs, computer will then close FP relay full time until key is off or RPMs drop below 400.
This is a safety feature to prevent electric fuel pump from pumping out gasoline in the event of a broke fuel line(accident) or roll over.
No RPMs = no fuel pump power

You can turn the key on and off and fuel pump will run for 2 seconds each time, so Prime the system multiple times to build up pressure.
The test light will tell you if fuel pump is getting power for those 2 seconds and if power is being cut while driving.

Fuel Pressure Regulator(FPR) is set for 42psi pressure at the injectors
FPR is hooked up to the Return line going back to the gas tank, it has a spring hold the valve inside closed until pressure gets to 43psi then spring is pushed open and excess fuel/pressure goes back to the gas tank.
FPR also has a Vacuum hose attached, this helps keep the fuel pressure at the injectors stable at about 35psi when engine is running.
High Vacuum in the intake means low demand for fuel to the engine, i.e. idling, so vacuum assist pulls the FPR valve open earlier than the 42psi.
Low vacuum occurs during acceleration, high fuel demand, so not as much vacuum assist and pressure is equalized for engine demand at about 35psi
Engine will run fine with fuel pressure between 25 and 45psi, so approx.
(Heads up when reading about Ranger fuel pressure, 1998 and up Rangers use Returnless fuel system, which uses 60-70psi)

On the other end of the fuel system is the fuel pump, in the gas tank, it has a Check Valve/Back flow preventer builtin.
Basically just a flap that is pushed open when pump is on and then closes when pump is off to keep 20+ psi pressure at the injectors for restart, this pressure will hold for MONTHS, not hours days or weeks...........MONTHS.
That 2 second run time adds about 10psi pressure, so 30psi for startup.
Check valve can fail, so pressure drops to 0psi when engine is off
It is part of the pump not a separate piece
Cycling the key on and off several times can build up pressure again for starting, but it is a sign that the pump will need to be replaced.

Fuel fuel injector Rail on the engine has a test port, it looks like a tires Air Valve, because that is what it is, a Schrader Valve.
You can put a pressure gauge on that to test pressure

TPS(throttle Position sensor), this is located opposite the throttle cable on the upper intake, and it can start to fail and cause a NO START by turning off all the injectors.
It is a long shot so do this test first
Test that there is a no start by cranking engine
Unplug the TPS 3 wire connector
Try starting again

 

[cbxer55]

Mine has had the exact problems a couple times in it's life. Last time, I had it towed to my local Ford dealer, who found the fuel injectors were badly plugged. They ran a heavy cleaner mix through them, and it was fine for all of a week, then started doing it again. I started using E10 10% ethanol fuel after that, problem has not returned in eight months. Starts up immediately upon turning the key every time.

Ford described the condition as a glaze on the end of t he injector. When cold the glaze is hard, and the fuel has to beat a hole in it in order to start. Once warm it will start readily. After it sits, the glaze reforms and it gets hard to start until the fuel beats a hole in it again.

I've had to hook my truck to jumper cables and crank it until the cows come home to start when cold. Then once hot it starts right up. If I let it sit two hours, right back to square one. Last time this happened was in early January. As I said, it seems that the ethanol fuel seems to keep the condition at bay.